Pat, What is the dimension from input to output shaft and what does a pair of drives go for? A PM will work also.

Yes I would love to know because, you have really peaked my interest...I have never been hard on the boat, either out of the hole are @ WOT...but damn it sure would be nice to just hammer the chit out of it sometimes...:coolcowboy:

If money was not an object, I would go with a Weismann or Arnesen drive. I would not go with a #6. The #6 is just too heavy and inefficient... especially on such a finely tuned boat. I Love the RPM cat! Steve did an awsome job in its design and construction.



Could not have said it better myself.

#6's are even being used on the 21ft ski race boats.

Here is the nordic 21 ski race boat with a mercury 1200 and single 6 drive

Here is a thor with the nxt drive which is now available

John,

I just noticed that the trim tabs on the 21' ski race boat are mounted at 1/2 deadrise. This is what I am going to try next on my boat. I am pretty sure that they are running the long tabs on that boat because of the extra weight of the #6 drive.

Chris

p.s. hope you get feeling better soon

I think that the NXT drive might be a viable option also. RPM has set up a boat with one of these, and it worked well according to Steve. The weak link in this system would be the stock mercury tranny. An upgrade to a good Bam unit would be in order.

The guy with the twin turbo Thor that lives near me is running the NXT drive, and likes it. With his motor de-tuned to 1100 hp, by turning the boost down, his first test run was 133mph.

Chris

p.s. with the boost turned up... his motor produces north of 1800hp on the dyno.

So are you saying there is a guy that is putting 1000 pluss hp through and NXT drive I know they are rated for 800hp, what is the warrnty on the nxt, Steve did the Norway boat with a 662 (700) anda Nxt drive, they did a stage 1 upgrade on the engine and it runs great, maybe an option...:coolcowboy:

Great info here guys. Please keep the dialogue going. I am learning alot as Im in the same situation as RPM is.

When Tim (of OCM), and I were planning on doing the Stage II upgrade to his Thor (830 hp), we discussed with Mercury Racing about the weak link on the NXT drive, and they said that the Transmition was only rated at about 800 hp. Because of this, when the guy bought the Thor from Tim, with the intention of putting his twin turbo motor in it, we discussed the probable need to upgrade the tranny to a beefier unit. The drive itself will take much more than that according to Merc Racing.. I don't remember the specific number. So far, the stock tranny has lived at between 1100-1200 horsepower, with the new owner not yet turning up the boost because this is his first cat, and he is learning how to drive it.

Tim's Thor has hit a best of 124 to date with a Whipple Stage II upgrade, and a Hering prop. Being that his boat is full carbon fibre, it accelerates extremely hard. I have never been in a boat that accelerates sooo hard! I think that John Lamont's boat probably handles better because of the slightly different hull, and the greater weight.. I have ridden in both.

The guy with the twin turbo Thor (cant remember his name), has a standard layup hull and therefore is pushing a lot more weight than your RPM cat is. I think that the NXT with a good Bam tranny would be a hot ticket.

Those big props are sure spendy though... $4500 or so

I heard that the 662 RPM boat did about 114-116 with a Stage I kit on it. A stage I should be about 760 hp on that package... pretty darn fast per horsepower.

Hope this helps,

Chris

p.s. I still think that the SCX upper, with a SC lower, is the best bang for the buck

Thanks fo the info, you really need to take a ride in my RPM if you want your a$$ pined in the seat while going around a tight curve, you are not going to find a better boat...I have a buddy that has a Thor down here and he has driven my boat and is pissed, if the market wasn't like it is he would sell his and buy one tomorrow, plus my boat was alot less in price than his stock 525 boat:lolhit:...but yes the NXT is something I should look into..:drink:

I added some more info in my above post.

I went and drove Steve's boat... absolutely loved it!!

If I could sell my boat right now.. I would have Steve build me one in a heartbeat.

Because of the economy...
I will just have to settle for my 95mph, open bow, wake boarding boat..

For now... :D

Chris

Well broke the clutch shaft again 44 hrs, and the upper gears were just about shot 78hrs, I am going to have to do something I don't know how much easier I can be to the drive, I am babying it now...:party-smiley-004:

Baby it down to Cumberland this weekend with us. :evilb:

Yea I hear you are going to be the star @ the run:coolcowboy:just get the fuk out the way when the big boys take off are you will be fish food, those boys cruise @ what we run WOT so be careful.

And the drive issue will get resolve over the winter just got the price on my drive 4600.00 bucks fuk that with the shipping to them thats 5,000 for an upper gear set and clutch shaft, chit just send me a new drive WTF, anyhow keep me posted on your SCX because I am leaning toward that over anything else, due to the cost and setup issues I am not going to spend 10,000grand a year on drive rebuilds hell I buy a stock Bravo and use the warranty every time it breaks, then sell it and buy a new one...it would becheaper:angry-smiley-038:

Well you and Steve have a good time this weekend and be careful, I would be there but I have Mark and his wife coming down from Al. and alot of other friends coming down for our end of summer Lake Bash always a good time...

sounds like fun

http://www.offshoreonly.com/classifi...o28713-en.html


There's a link for you :drink:



Jon

The wet-sump #6's eat more horsepower than the dry-sump #6's, and even they are too heavy and power eating.

Just my humble opinion,

Chris

p.s. Im sticking with my SCX suggestion

I may be wrong but arent the clutch shafts the same in the "bravo" type drives???

My drives do not have a fixed x dimention.

15 inches is the WMD

10.5 is the WSD

4.5 is the WDP

We never line up the crankshaft to the input of the drive so it really doesn't matter what they are. When I went to put a WMD and a WSD on a small boat I had the prop where I wanted it and the gimbal was above the transom. So finally I designed a very short X dimention drive, The WDP.

When we replace a #6 we use a 5.5 inch offset box to get to the 18 15/16 x dim.

When I see a 19 t spline propshaft I do not think of a drive you can hammer.

pat W

The scx has its own shafts and they are twice as big a s a bravo drive. There are a few single engine cats running 1200 hp thru these drives with 0 failures to date.

Correct.. The SCX clutch shaft is considerably bigger than a bravo xr.

John is also correct on the stats for the single engine cats.

Chris

Talked to IMCO today, the only failers that they have had are shifting @ higher @ RPM, above 800 other than that they told me knock on wood no problems, I can use my MMW lower on the drive I will just have to go with a lager upper shaft and it will all mate up to the upper, this is really looking like the rout that I am going to take. Don't get me wrong, I love the MMW drive and it has really heldup better than I exspected but I am just looking for more reliablity out of a drive, so if anyone is interested I will be putting the drive up for sale on the Classifieds, FYI every thing in the upper is brand new, all new gears, clutch shaft and all bearings, and races, they also upgraded the billet top cap with larger studs and nuts to ad even more rigidity and reliablity...a new drive is 17,000 pluss dollars top and bottom I am working up a price but the drive will be back Friday I will take pics and post on the classifieds:kiss:

Smart move in my opinion.

You can re-coup some of the cost of the SCX upper by the sale of your MMW upper.

Are you saying that the MMW lower will mate up to the SCX upper by using IMCO's conversion shaft?

If so... that is great news!

Chris

Yep, The boat loves the MMW lower, I ran an bmax with the short lower and it spun out @ 60...running the MMW lower, lets just say @ 80 in a u-turn I chickend out I figured 80 was fast enough for testing, plus I don't think I could have held on pulling any more g's:drink:

Not really worried about the cost, just looking for longevity, and peice of mind:coolcowboy:

I would still get away from the bravo style lower,I run 1050 hp 1000 plus ft lbs of tq and I never get 75 hours out of lower bravo gears even with the best preperation, cryo finish etc.
Something else reading your post,this may even be a non-issue since you are going to a different drive but for the guys stuck running bravo drives 75 hours is waay to long to go between tear downs and inspections on a bravo drive behind big power. I change the oil in mine every 10 hours and tear it down and inspect everything at least every 30-40 hours or less if I start finding metal in my oil. In 9 years of running various blower motors from 650 hp,then 750 hp then 950 hp and now 1050 hp I have never blew the teeth off a upper gear or destroyed a case. I have found bearings just starting to fail,clutch shafts that were fractured,lower gears that were on the verge of total failure etc. Many of these problems I found would have led to total destruction of the upper or lower IF I hadn't caught them,fyi,Smitty

...Or you could switch to a Weismann drive and get rid of all that aggravation...

I don't go 75pluss hours on teardowns, the clutch shaft won't last but 40hrs so far the drive blew all the gears @15hrs, put drive back on @ 24hrs, clutch shaft broke @ 66hrs shaft changed all gears magnafluxed all was good, clutch shaft broke again @ 101hrs gears check, they were fixing to let go all is new now, so I am going to get the drive back tomorrow and put it up for sale, someone will be getting a good deal since it is a new drive except for the case..:grinser010:

Got 35,000 that you want to loan me:coolcowboy:really wish I would have went this way during the build...:angry-smiley-038:

I didn't know it would cost that much. :eek: :( I see now why all of a sudden you quit talking about them, and why you're staying with the Bravo style.

Just look at it as an investment. a good one.

pat W

I havent stop talkig about them, I really would love to have the weisman, Hey Pat does Weisman have 6 mo no interest:lolhit: but seriously I haven't ruled anything out, if I do a SCX it will only be until I can get the funds for the Weisman, like I said on other post, Pat is the final desision, just want him and Steve to work out all of the details on instalation and an exact price for all of the goodies:drink: be working on me a brother-in-law price Pat.

Again thanks for all the help Pat, as soon as we can work all of the details out, should be a hell of a combination, BTW how much speed increases should I look for if any with the Weisman...:drink:

Ah so, straight from the Coon-ass's mouth. :cool-smiley-027:

I think you'd see at least 5mph, maybe 10, but Pat could tell you better than I.

:ernaehrung004:

132mph w bravo.....

What Rpm?
What prop(dia, # of blades pitch)?
What ratio?
What is the redline on new engine vs old?
What trim position(pos,neg or even)
Were you out of engine or Euevos?

pat W

Well Pat I have plenty more Euevos, I was out of prop...

RPM 6400
Prop custom 36 labbed done @ lake X for RPM
ratio 1:36
engine redline is 6500
no clew I run by feel and by ear
and again I believe it had just couple of MPH left water was flat and my nuts were just starting to change color:drink:

here are a couple of photos, 1 of Garminn and Livorsi showing 129, and another run when garmin battery died...

129 @ 6400 with a 36?

20% slippage.. Yuck.

Even calculating it as a 35 pitch (which is what you usually do with merc props) it equates to about 18% slip.

Not to be disrespectful in any way..But..

what is the big deal with that... I think that slip is over emphasized. Many boats run the fastest at between 15% - 20% slip.

Gary Taylor ran about 20% slip while setting the world speed record for a single engine v-hull.

The "cat-killer" runs about 15% slip.

I have done literally hundreds of hours of testing on my boat, using different drives, spacers, and props. I have had my slip as low as 7.2% and as high as 22% on the top end, and my boat is the fastest and handles the best with slip between 14% and 16%. I had a naval hydrodynamics engineer tell me that I should stop being so focused on slip, and be more concerned with performance and speed. When I started doing that.. my boat started getting faster.

130 mph is darn fast for a single engine.. 26 ft cat.

Just my humble opinion,

Chris

Thats 129, and 132, and the best part about it is the a$$ end of the boat didn't want to swap ends at that speed:angry-smiley-038:like a single surface drive does, and 132 feels the same as 90...you can sit back and relax, it gets boring... trust me slip doesn't bother me @ all and it was a labbed prop...the boat comes out to around 16-18% slip, and it loves it...by the way do your math with any other cat 26' long that ways 5,000lbs with the same setup and it would be much slower:kiss:

Well said Chris:kiss:you hit the nail on the head, I had Hering tell me that they could get my slip down to around 8%...boat hated it did everything to get it to 120mph, swaped it out for a non labbed 34" Bravo and with 2 people and full of fuel boat runs 126. I quit using the labbed props due to the fact that I could only get a few hrs on them before they would start to come apart...ask Steve with RPM and read the Powerboat on the Redline where Bob Tegue states that the prop lost a blade tip and another started coming apart and the boat still ran 105 with 675hp, thats the 36" that I ran the numbers with:eek:(sorry Steve:drink:)